An enterprise has two edge routers to different providers, needing all outbound Internet traffic to exit via Router-A, return traffic for its public prefix to enter via Router-A, with Router-B strictly backup. Which BGP attribute design should the designer apply for coordinated path preference?

Outbound best-path is controlled inside the autonomous system where weight on the local router and local preference domain-wide can deterministically prefer Router-A, while inbound traffic is influenced by making the Router-B advertisement less attractive through AS-path prepending, preserving Router-B as backup without withdrawing the prefix. Using MED for outbound and local preference inversion fails by concept because MED influences neighbor inbound decisions, not local egress, and the direction is reversed. Tuning origin and shortening the backup path fails by concept because origin is a weak late tiebreaker and a shorter path via Router-B would attract inbound to the backup. Setting MED for outbound and lowering weight on backup fails by concept because MED does not decide local outbound and lowering backup weight still leaves inbound uncontrolled. For the exam, remember weight beats local preference locally, and prepending affects inbound only, and a practical check is to confirm egress with traceroute and ingress with external looking glasses.